Process of making solutions containing sulphuric acid and ferric sulphate



Patented Dec 1%, 31923,

entree arteries or reason, ARIZONA, assrdnon or catamaran 'ro cnannm'n.

v managea- Parana- @FFHCCQL VAN BABNEVELD, OF ST. LOUIS, MISSOURI, AND JNE-THIBD TO LAWRENCE R. 'ECK- raan, or Tucson, ARIZONA.

"raocnss or No Drawing.

To all whom it may concern: Be it known that I, ED ND S. LEAVER, a citizen of United-States, residing at Tucson,

in the county of Pima, in the State of Ari.

- 65 zona, have invented a new and useful Process of Making Solutions Containing Sul-.

- I have found that 'when material containing oxidized iron compounds, for example, calci-nes produced by roasting pyritic ores, are subjected to the action of gases containing sulphur. dioxide, together with a considerable quantity of air and in the presence of water, there is more or less sulphuric acid produced as well as more or less ferric sulphate. The pulp through which the gases containin sulphur dioxide and air are passed will in general containferrous suleration of a sulphating roast or from the action of more or less sulphuric acid and ferric sulphate already produced-on the ferric oxide 1n the calcines. The action of sulphur dioxide and air in ferrous sulphate in the resence of water causes production of ferric sulphate and sulphuric acid. According to my invention, this reaction is utilized for the production 'of a solution containing sulphuric acid and ferric sulphate for leachingland other properties. r y invention may be carried out in the following manner: The calcines from a roasting furnace, such calcines having, for

roast, are reduced to a suitable state of division and by crushing, grinding or otherwise, water being added during grinding or subsequently to form a pulp. This pulp is thensubjected to the action of gases containing G SOLUTIONS CONTAINING SULPHURIC ACID AND ii} SULPHATE.

phate resulting either directly from the op-.

example,. been subjected to a sulphating Application filed march 29, 1 922. Serial No. 547,825.

diom'de through aporous medium into water or ulp containing the ferrous sulphate to e ect a fine division of the air passing into the solution, or pulp. The air containin sulphur dioxide may be bubbled throng the sol'ution, being admitted by an air jet-producin more or less violent agitaco tion of the solution and bubbling of the gas.

2. The air containing sulphur dioxide I may be beaten into the solution of pulp by means of mechanical agitators, such as are used in flotation'operation.

3, The air containing sulphur dioxide may be brought into contact with the pulp by passin the air in 'countercurrent with the pulp t rough a rotating drum in a man ner substantially as set forth in Patent No.

1,312,488, issued to Inc August 5,1919.

The gaseous'medium containing air and sulphur dioxide may constitute the efiuent of a roasting furnace or it may be generated by means of an ordinary pyrite burner or sulphur burner using suflicient air to give the required dilution of SO gas. I have found that in order to effect the described operation, which is essentially an oxidizing operation, it is desirable to provide a sul-' phur dioxide concentration in the gas of less than one-half of 1 per cent. In any case, the sulphur dioxide content of the gas need not be more than 5 per cent, since with aconcentration of that amount the'ferric sulphateis completely reduced to ferrous sulphate with substantially complete production of sulphuric acid. The reaction maybe regarded as taking place in such manner that the ferrous sulphate is oxidized in the presence of sulphur dioxide and air to form ferric sulphate and the sul hur dioxide then breaks down part or all t e ferric sulphate in the presence of water forming ferrous sulphate and sulphuric acid, as shown by the fol owing equations:

. (a) 2FeSO +SO +O =Fe (SO 2( i)3+ 2+ 2 2FeSO +2H SQ I The presence of sulphur dioxide accel-- erates the oxidation of ferrous iron and the percentage of SO present affects the rapidity with which the ferric iron breaks down for the formation of sulphuric acid. When the concentration of the sul hur dioxide in, 11%

thegas entering or bubblin through the solution containingferrous iron is less than ispracticable to'change all of the ferrous iron to ferric iron with the formation of some sulphuric acid. As .the percentage of sulphur dioxide in the entering gas increases, more ofthe ferric iron s broken down so-that a concentration of sulphur diill oxide can be attained which will effect a complete reduction of all the ferric iron to ferrous iron with production of a corresponding amount of sulphuric acid. 7 By suitably controlling the concentration of the sulphur dioxide in the gas applied to the operation, the proportion of ferric sulphate to sulphuric acid in the final solution may he varied according to the requirements of any particular case. The rapidity of the oxidation is directly proportional to the volume of gas. With 0.5% iron insolution as ferrous sulphate, 10 volumes of 0.5% sulphur dioxide gas per minute to one volume of solution will oxidize all the iron to ferricand at the same time will form nearly 1 sulphuric acid in about two hours. With 1% ferrous iron and other conditions the same; it twin require about 4: hours to make 1% ferric iron and 2% sulphuric acid. By arranging apparatus in series it is practicable to utilize 90% of sulphur dioxide. Reaction (A) is retarded in the presence of free sulphuric acid. Maximum oxidation is obtained in neutral solutions.

The solution obtained as' above described and containingsulphuric acid together with ferric or ferrous iron or both ferric or ferrous iron in any desired proportion, can be used as a leaching agent, for example, in the re- .covery of copper from oxidized ores or sulphide ores or mixtures of oxidized or .sul-' phide ores. The lixivium is especially advantaigeous when applied to mixed oxidized and sulphide ore's as the. sul huric acid constituent will serve to disso vs the oxidized ores and the ferric sulphate constituent will serve to dissolve the sulphide ores.

i closed-"in my patent aforesaid, the presence of ferrous sulphatein the solution as, it on 7 tion results.

By carrying out the process in the leach ters the leaching drum produces sulphuric acid at no additional cost and makesthe leaching recovery of copper from high siliceous ores practically complete.

When iron is used as a preci itant for the Cu the return solutions furnis the ferrous sulphate at no cost. With the formation of ferric iron within the drum or by an auxiliary method before entering the drum it is in some cases possible to extract both sulphide and nonsulphide copper by leaching in the shine operation. 7 4 V This process of making ferric iron may be applied in making ferric ammonium sulphateoand other salts, eliminating the use of nitric acid asanoxidizer and avoiding the subsequent step of its removal, thereby cheapening the manufacture of these salts. For example, into a solution of ferrous sulphate, air containing 0.5% (or less) sulphur dioxide may be assed until complete oxidafl his will be indicated by change in color of the brownish-red solution to lemon-yellow. If the solution is then evaporated down to the desired specific gravity, the required-amount of ammonium sulphate added 'and'the solution allowed to cool, the crystals of ferric ammonium sulphate may he filtered out.

What I claim is:

l. The process of making a solution containing sulphuric acid and ferric sulphate, which consists in sub ecting material containing ferrous sulphate in the presence of containing not more. than 0.5 per cent of sulphur dioxide. 3. The process which consists in subjecting material containing ferrous sulphate in the presence of water to the action of sulphur dioxide and air to produce ferric sulphate' and then acting on the ferric sulsubscribed my name this 13th day of March, 1922.

EDMUND s. LEAVE'R.

till

phate with sulphur dioxide in the presence 

